More than 130,000 cases of colorectal cancer are diagnosed in the United States each year, and over 50,000 deaths result from it, making this form of cancer the second leading cause of cancer deaths. The lifetime risk of developing colorectal cancer is about 1 in 20. Although this disease is treatable if diagnosed early by colonoscopy, most people with colon cancer have no symptoms, initially. Once a cancer has spread beyond the primary site of origin, the five-year survival rate is only slightly better now than it was 30 years ago and 90% of tumors metastasize. Tumors are genetically unstable and heterogeneous and can become drug resistant. To improve treatment for colorectal cancer and cancer in general, new therapeutic targets must be identified and representative animal models are needed to develop and test new concepts of cancer cell proliferation and metastasis. Immunodeficient mice have played an important role as host for cancer xenografts. However, variable survival, the need for a significant number of cells for injection, costly maintenance and lengthy assay time make them a problematic model for cancer research. This SBIR aims to develop zebrafish (Danio rerio) as an alternate in vivo xenograft model for growing human colorectal cancer cells and for screening potential drug candidates. Cell proliferation, embryogenesis and patterning will be assessed. [unreadable] [unreadable] [unreadable]